Battery driven setup
larsbrinkhoff opened this issue · 8 comments
Hello,
I'd like to make something similar to this, except it supposed to be a wall-mounted clock. I would like it to be powered off batteries instead.
Do you think there are low-power parts that can replace those you used? I do need a 32-bit CPU running Linux in there, but it doesn't have to be quite as fast as an rPi. I suppose the display draws most of the power anyway. Monochrome without backlight is fine.
Thanks!
E ink? OLED?
Hello Lars! Interesting inquiry!
So I assume you need something that is not expected to be updating or interacted with constantly and should last about a month (otherwise it is not fun, or is it?) on batteries. If you get a 10,000mAh powerbank you'd need your system's average consumption to be around... 15mA!
The single board Linux with the lowest consumption that I have used are the Raspberry Pi Zero and the Onion Omega. However they consume around one order of magnitude more, i.e. ~150mA. The worst part is that they lack a PMIC so there is little one can do to decrease that, by suspending to RAM.
My first suggestion would be to go for something that suspends to RAM in a really low power mode, but I could not find conclusive evidence of a specific board capable of this. The Beaglebone boards seem to support suspension to RAM but I could not find anything about the consumption during that state.
Therefore, due to the lack of a better and concrete solution, I would suggest a microcontroller periodically turning on the Linux machine.
Finally, I think an e-ink display is a must in any case, so to get the screen's consumption out of the equation.
Thanks!
Looks like I have to forego the battery. In my intended application, there should be a PDP-10 emulator running continuously. And I don't want to change/charge batteries every week.
Though, I hear Tesla makes large batteries...
I just saw what's this about. Cool! Unfortunately I do not think turning the computer on and off makes sense if you need to update the display every minute. 😓 I had in mind a way slower refresh rate.
Every second, probably.
I think the processor could run somewhere around 100 MHz. That might help.
I believe the operating frequency is not the most important factor, but rather the ability of the processor to pull the system into a really low power mode when not updating the screen. This is very easy to do with microcontrollers, but unfortunately I do not think it is possible/easy with what you are trying.
OK, while writing I got an idea! What about this setup: An inexpensive and low consumption movement sensor, that triggers a microcontroller to power on the Linux system when someone is actually around? For movement sensing I have the following options in mind:
- PIR sensor: Detects whatever is moving within the line-of-sight towards all directions.
Or if you are feeling adventurous...
- Microwave radar: Should be able to detect movement through walls, so you can turn on the system even before someone walks in the room!
I have tried one of these radars out, was not super satisfied with their performance but admittedly did not spend enough time to figure things out. I think they have a lot of potential.
From the user's perspective, the system is continuously on!
Good thinking outside the box, I like it! Also bonus points for involving a microcontroller. :-)
I see now there are lamp sockets on the walls, so I probably won't need a battery.